• on Computer/Software/Internet
  • Published in issue 11/2014 on page 10
About the article

USB Hub feat. RS-232/422/485

3 x USB, 4 x serial port, 0 x microcontroller

USB Hub feat. RS-232/422/485
Since the DB25 / DB9 serial port has disappeared on modern PCs, it is getting complicated to connect up legacy equipment with RS-232 connectivity. Sure, there are worthwhile workarounds, but these tend to be limited by annoying drawbacks—in particular where multiple devices need to be connected. This was what driving force to design and present this universal converter with its two RS-232 ports and two RS-422 ports.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.
Component List
(SMD 0805)
R19,R20 = 10Ohm
R19,R20 R21,R22,R23,R24,R25,R26,R27,R28,R51 = 22Ohm
R10,R11,R12,R13,R14,R15, R16,R17 = 47Ohm
R8,R9,R64,R65,R66,R67 = 120Ohm
R53,R54,R55,R56,R57,R58,R59,R60 = 330Ohm
R18,R37,R38,R39,R40 = 510Ohm
R23,R27 = 10kOhm
R1*,R63 = 1kOhm
R50*,R52 = 1.5kOhm
R6 = 2.2kOhm
R61 = 4.7kOhm
R3,R4,R5,R7,R62 = 10kOhm
R2 = 12kOhm 1%
R29,R30,R31,R32,R33,R34,R35,R36,R41,R42,R43,R44,R45,R46,R47,R48,R49 = 15kOhm
* do not fit
(Default: SMD 0805)
C13,C16, C17,C32,C35,C36,C37,C38,C39,C40,C41,C42,C43,C44 = 22pF
C1–C4,C7,C8,C10,C11,C12,C14,C15,C18–C31,C33,C34,C61,C62 = 100nF
C45–C51,C54,C57,C60 = 1µF
C9 = 3.3µF 16V tantalum (E)
C53,C56,C59 = 4.7µF
C5,C6 = 4.7 µF 10V, tantalum (A)
C52,C55,C58 = 68µF 6.3V, tantalum (D)
L1,L2 = ferrite, 70Ohm @ 100MHz, SMD 1206
D9 = B320A-13-F
IC1 = FT4232HL
IC2 = LM2937ES-3.3
IC3 = 93LC46B-I/SN
IC12, IC13 = SN75240PWR
IC4, IC5, IC11 = MAX3243EIDW
IC6 = 74HC595D
IC7, IC8 = MAX489CSD
IC10 = TPS2044BD
LED6,LED7,LED8,LED9,LED10,LED11,LED12,LED13 = LED, green, 3mm
LED1,LED2,LED3,LED4,LED5 = LED, red, 3mm
T1 = BC817-40
JP1,JP2,JP5,JP6,JP7,JP8 = 2-pin pinheader, 0.1” pitch
For JP1 and JP2: 120Ohm termination resistor for RS-485 (optional, see text box)
JP3,JP4,JP7,JP8 = 3-pin pinheader, 0.1” pitch
Jumpers, 0.1” pitch, for JP1-8
K1 = USB-B receptacle, right angled, PCB mount
K2, K3 = 9-pin sub-D plug
K4, K9 = 5-pin pinheader, PCB mount, 0.15” (3.81mm) pitch
K5 = barrel jack supply socket, 12V/3A with switch, 0.075” (1.95mm) pin
K6, K7, K8 = USB-A receptacle, right angled, PCB mount
X1 = 12MHz quartz crystal, SMD
X2 = 6MHz quartz crystal, SMD
Case, ABS, 65x180x120 mm e.g. VERO 75-265742
PCB # 140033-1-v1.2
Ready assembled unit: # 140033-91 [2]

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